How to partition a Mac hard drive or SSD, or create a APFS volume

Here's how to split your Mac hard drive into multiple partitions or volumes so that you can run more than one OS on your Mac, or divide up your Mac so different users can have their own space. We'll show you how to create a volume in Mojave and High Sierra, how to create a partion on an older Mac, and we’ll look at how you can use Boot Camp to install Windows on your Mac

There are lots of reasons why you might want to partition your Mac. Perhaps you want to partition your Mac to run Windows, or maybe you want to install Mojave beta on a partition, so that you can run both the beta and the full version of Mojave, alternatively you might want to keep High Sierra on your Mac but install Mojave on a separate partition so that you can use apps that might not work in Mojave or its successors.

Another reason why you might want to partition your Mac is so that you can create a partition for Time Machine to back up to, alternatively you might want to create separate partitions for the different people who use a Mac, essentially creating multiple Macs in one box.

There are a few factors that will determine how you go about your project. The most important point is to establish whether you will even need to create a partition, or, if you can just create a volume on your Mac. (This is a little confusing, because essentially a volume and a partition are the same thing, but newer versions of the macOS handle things differently enabling users to create a volume and use it in the same way as a partition would have been used, but without any of the complications of having to wipe the Mac and start from scratch).

If you are running High Sierra on a Mac with a Flash drive, or Mojave on any Mac then you don’t need to create a partition at all, you only need to create a new volume. This is thanks to the new Apple File System (APFS) which replaced the old HFS+. APFS has a number of advantages over HFS+ one is Space Sharing, which makes it possible for the available space to be shared between the different volumes on your disk. That space can be made available to all the different volumes at any time, rather than being assigned to them when they are formed, as is the case with a partition.

In this article we’ll show you how to create a volume in Mojave and High Sierra, how to create a partion on an older Mac, and we’ll touch on how you can use Boot Camp to install Windows on your Mac - although we have a feature dedicated to doing that here: How to run Windows on your Mac.

You may only have one Mac, but you can set it up so that it has multiple personalities…

Before you start there are a couple of things you need to do.

Back Up just in case something goes wrong

Delete files and applications you don’t need to make lots of space

How to create a volume in High Sierra or Mojave

It’s really easy to ‘partition' your Mac in High Sierra (if you have a flash or SSD) or in Mojave thanks of APFS. While you can still partition your Mac, you don’t have to, you can just create an additional volume using Disk Utility.

If you do try to create a partition using Disk Utility in these versions of macOS you will see the warning: “APFS volumes share storage space within a container, occupying a single partition. Adding and deleting APFS volumes is faster and simpler than editing a partition map,” which, it has to be said, sounds more complicated than it is.

Needless to say, the best and simplest option is to Add a volume, so follow these steps:

Open Disk Utility.

Click the drop down menu beside the View button in the toolbar and choose Show All Devices. This will make sure you can see the volumes within your disk. It’s likely you have one called Home.

Select the Home volume, and double check that it is an APFS Volume (it needs to be for this to work).

Now all you need to do is click on the + button above Volume in the menu to create your new Volume.

Give your new volume a name, we called ours Test, but you might want to call it Mojave or Beta, if you were planning to install that version of the OS on that volume.

You can now choose to set a storage limit for this volume, but you don’t have to. If you want to, click on Size Option and fill in the Reserve (minimum) and Quota (maximum) options. Remember you will actually need to have enough space available on your Mac to allocate this way (which is why we started by advising you to delete things from your Mac!)

Now you can click Add and your new Volume will be added to your Mac.

You could just attribute that volume to a family member or colleague to use so that you don’t mix up your files, but a popular scenario would be to use this volume to install an alternate version of the Mac operating system on. We have a detailed tutorial on installing two versions of macOS on your Mac here (How to dual boot two versions of MacOS, but in summary, here’s what you need to do:

Download the installer for the version of the macOS or macOS beta you want, just don’t install it yet. (You can check to see if the installer is already downloaded by searching for it in Spotlight, press Command + Space and start typing the OS name).

Now click on the installer, but make sure you choose the new volume you created as the destination for the installation.

Wait while your Mac installs the new OS on that volume.

Once it’s done it should open up in the volume with the new OS installed.

When you are ready to go back to your old version of the OS, just shut down your Mac, and reboot with the Alt/Option key held down.

Choose the ‘partition’ that has the version of the OS on it you want to run and your Mac will boot up in that.

Partitioning a Mac

If your Mac isn't running Mojave or you are using High Sierra on a Fusion Drive, or if you can't update your Mac (or dom't want to update your Mac) to either macOS, or even if you are using Mojave or High Sierra, but you don't want to go down the Volume path, prefering to create a firm partition on your Mac, here's what to do. (This section includes original reporting by Kenny Hemphill).

As we touched on above, partitioning a hard drive, or an SSD drive, involves creating multiple volumes from one physical storage medium. The volumes appear separately in the Finder and are treated separately by your Mac. You can format them independently and use them for different purposes.

Why should I partition my Mac?

There are several reasons why you might want to partition your Mac's hard drive. Historically, the most common was to separate the Mac's system files from the volume on which data was stored. These days MacOS keeps your data in your Home folder, or even in iCloud, so it's a far less common scenario.

Now it's more likely that you'll partition a drive in order to run multiple operating systems, or multiple versions of the same operating system, on a single disk. That's how Boot Camp works, by partitioning the drive and allowing you to install Windows on the other partition.

As we said above, you could also partition your hard drive to allow you to use Time Machine to back your boot partition to a different partition on the same disk. To do this, however, the Time Machine partition has to be at least twice the size of the volume you want to back up, leaving you less than half the total disk capacity to work with.

In addition, storing a backup on the same disk as the one being backed up carries several risks and should only be done as a convenient method of restoring older versions of data. Your real back up should always be on a separate disk.

How to partition your Mac using Boot Camp

If you plan to use Boot Camp, you should run Boot Camp Assistant and follow the instructions to partition the drive and prepare for an installation of another OS.

You will need at least 40GB of free space available.

Follow the instructions on the Boot Camp assistant to install Windows.

How to partition your Mac using Disk Utility

Before you start, you should back up the drive you intend to partition, you could use Time Machine, or you could clone it using a tool like Carbon Copy Cloner. Assume the worst will happen and you'll lose all the data stored on the drive when you attempt to partition it. Make contingencies. A bootable clone will have you up and running again in no time.

Once you've cloned the drive and verified you can boot from it by restarting your Mac with the clone plugged in and selected as the Startup Disk in System Preferences, you're ready to begin the process of creating a new partition, follow the steps below.

Unplug the disk with the clone on it and restart your Mac as normal.

When your Mac has restarted, press command+Space and start typing Disk Utility, or find the application inside Utilities in the Applications folder. Open Disk Utility.

In Disk Utility select your Mac's internal drive, making sure to click on the drive and not the volume beneath it. You should see two tabs below the toolbar: First Aid and Partition. Click Partition.

Click the '+' below Partition Layout to add another partition to the disk. You'll see the layout change to show the additional partition. You can now change the size of the partitions by dragging the line dividing them up or down, subject to a minimum size for the boot partition which is dependent on the data you currently have stored on it. When you've made them the size you want, click on the new partition and type a name for it in the 'Name:' box. Make sure the format is Mac OS X Extended (Journaled).

Once you've set the partition sizes and named the new partition, click Apply to finalise everything. Alternatively, if you change your mind or want to start again, click Revert instead.

Your Mac's main drive is now split into two volumes, with the new one empty. You can now install a different version of OS X on it, use it to install a public beta of macOS, or keep it as a place to store data.

You can re-size the partitions at any time using the same process you used to create the new partition, but instead of clicking '+' just drag the partition bar up or down. The degree to which you can re-size will be dependent on the data stored on each partition.

When you've created your new partition, you can install an operating system on it by double-clicking the disk image (read about how to get old versions of macOS and Mac OS X here). Select the new partition as the location for the installation. Then follow the instructions to complete the installation. Once it's done you can reboot into the partition whenever you need to.

The risks of partitioning a Mac

The only real risk when you partition your hard drive is data loss. You can mitigate this risk by backing up or cloning your disk before you start and whenever you re-size partitions.

How to resize and change your partition size

Through Disk Utilities you can also change the size of your partition, where you can extend it and sometimes even shrink it, depending on the amount of data free on your drive.

To change the size of the partition, simply click on the partition segment within Disk Utilities and press the plus '+' or minus '-' button to change its size.

If you're removing the partition and want to re-allocate the space to your primary drive, then you'll need to first click on the partition and select Erase, so make sure you have a backup of the data. Once you've deleted all the data on the drive, click on the partition again and press the minus '-' button. This will now re-allocate the disk space to your primary drive.

If you're extending the partition, make sure you've got enough space on your primary drive to accommodate the changes in size. Simply press the plus '+' button to extend the size of the partition.

Once you make changes, you Mac will take a little while to apply the changes. As soon as the process is complete you'll be presented with a green tick indicating the 'Operation sucessful'.

The alternatives to partitioning a Mac

If you don't want to partition your main disk, there are other ways you can safely run a different version of macOS (or OS X) or a beta of a new version. One option is to install macOS on an external hard drive, or even a USB stick. You can then boot from that, either by selecting it as the Startup Disk in System Preferences, or by holding down the Alt/Option key during startup and selecting it when prompted.